The invention relates to a display device, comprising an illumination means and a liquid crystal display.
Display devices comprising liquid crystal displays (LCDs) have been used for many years in many different fields of technology. They are widely used for example in television sets, computer screens and mobile phones.
An important parameter for the quality of the image representation by means of a liquid crystal display, in particular when representing moving images, is the response time of the liquid crystal display, wherein the response time specifies the time duration which is needed for a pixel of the liquid crystal display to move from a first given state to a second given state. If the response time of the liquid crystal display is too long, a in-motion unsharpness (the so called, motion blur') occurs when representing fast moving images, which is conceived as disadvantageous by a viewer. Accordingly, there exists a great need for providing liquid crystal displays with the shortest possible response time.
Further, it is well known that the response time of liquid crystal displays is temperature-dependent and increases with decreasing temperatures, in particular in the temperature range between ca. −40° C. and 0° C. In order to ensure an image representation even in such a temperature range, it is therefore required to compensate or prevent the temperature-dependent increase of the response time.
In this context, the document EP 1 973 092 A2 proposes a method for a display device comprising a liquid crystal display, wherein an improvement of the response time of liquid crystal displays is achieved by multiplying the applied voltage, which is necessary for the change of state of a pixel of the liquid crystal display, with a specific factor, the so called, overdrive parameter'. Yet it is unfavorable of this method that the overdrive parameter to be used are temperature-dependent and therefore either have to be determined by very extensive calibration measurements or have to be estimated by means of complex algorithms, thus rendering the proposed method comparably time-consuming and/or computationally intensive. Furthermore, measurements show that this approach is virtually ineffective in the temperature range between −40° C. and 0° C.
In contrast, the document EP 0 438 093 A2 proposes a display device comprising a liquid crystal display, a temperature sensor and a heating means, wherein temperature changes of the liquid crystal display are monitored by means of the temperature sensor and compensated by means of the heating means, thus ensuring a working temperature which is suitable for the liquid crystal display and thus ensuring an essentially constant and suitably short response time of the liquid crystal display. This display device is disadvantageous because the usage of an additional heating means results in higher costs and decreases the transmission of the glass and thus the optical light output ratio.